''Nah, I'm not afraid,'' he says with six-year-old bravado. ''I know my address in El Salvador. I'll be all right.''

They say Salvadoran children grow up fast these days.

Carlos and his father had embarked on a trip taken by hundreds of thousands of Salvadorans over the last few years - following a route they hoped would take them out of El Salvador's civil war, away from attacks on villages and marketplaces and the horror of night raids into homes of friends and loved ones.

Most of these Salvadorans try to steal quietly into the United States; many then beg for asylum. But along the arduous trail across Guatemala and Mexico - and even once they cross the US border - the Salvadorans say they find officials not particularly sympathetic. Some refugees tell stories of being robbed and beaten. They express fear that if they are sent back to El Salvador, they will be killed. ''Please help us, please. You're our only hope,'' a Salvadoran woman sobs to a priest in the Nogalas prison. Her whimpers are not calmed by his reassuring murmurs. For what can he do, what can anyone do for someone who has lost identity papers?

It's common belief among the Salvadorans that a person without papers, without money, dumped on the Guatemalan border is likely to be shot. From Nogales, many of the Salvadorans are bused by Mexico to the Guatemalan border.

About 20 other Salvadorans awaited deportation the day of this reporter's visit. They passed the time between now and uncertainty huddling on a few mattresses on the floor or leaning against the wall with Carlos and staring into space.

Almost all had been picked up the day before at Benjamin Hill, a checkpoint close to the US border. The details of their stories vary, but the substance remains the same.

In El Salvador they had been campesinos - peasants - or lower-middle-class workers such as bookkeepers and shoe salesmen. Many were active in churches and, with a few exceptions, they said they had been apolitical. But in a country where more than 30,000 people have been killed or have disappeared since a military-civilian junta took over in 1979, even to be nonpolitical is political.

To belong to a labor union, to be a student, teacher, a religious lay leader - even to be a male between the ages of 13 and 30 - is dangerous these days, they say, for it draws the military's attention. It invites a sudden visit in the dead of night by anonymous men.

No one ever claims responsibility for the mutilated bodies found almost daily by the side of the road, but Salvadorans in the Nogales prison claim torture is the signature of the government. (Some analysts counter this charge saying the most brutal acts are commited by paramilitary security forces over whom the government has little control.)

Even those who belong to no organization and ask no questions sometimes cannot escape the day-to-day fear of death, the anonymous threatening letters to friends and relatives, the unexplained machine gun blitzes in the marketplace, and the shattered economy. And so, they say, they have to leave.

To escape, some Salvadorans become refugees in their own land, migrating to the dubious safety of crowded government camps near the capital city of San Salvador. At least a half million others have fled to countries in Central America that are having their own troubles: Nicaragua, Guatemala, Honduras.

The prisoners in Nogales are a fraction of the hundreds of thousands who have headed for the security of the US and the large refugee communities in Los Angeles, Washington, Houston, and other cities. To them the US means safety from meaningless death and a chance for a job. Some are looking only for a temporary haven until life at home gets better; others want to stay here permanently.

The road to the US is not easy, they say. With tension in Guatemala increasing daily, indiscriminate killings there are becoming more and more commonplace. Mexico presents a different set of dangers:

''Salvadorans are very profitable here,'' one says bitterly. He asserts that customs officials and border patrols find the homeless eager to avoid trouble at all costs. Two sisters, about age 17 and 19, tell a typical tale.

"Our father took out a loan on our house to send us away to the United States ,'' says the elder, her feet sliding awkwardly in cast-off sandals a size too small. ''When we got to Mexico City we were stopped by officers in green uniforms with badges. They said to give them all our money or they would rape us. When we asked what we were supposed to do with no money, they said (prostitution).''

The girls managed to make it as far north as Benjamin Hill but were caught by the double checkpoint that many refugees say operates there. Salvadorans are stopped at the first checkpoint, shaken down for their valuables, and allowed to continue. The guards then call ahead to the second checkpoint a little up the road and the refugees are picked up there and arrested.

''They didn't tell me I was arrested,'' says a woman who has been listening expressionlessly. ''I gave them some money and they said I had to go into Nogales to get new papers to continue. They said I had to take a taxi into Nogales and it would cost 1,000 pesos (about $40). I paid the fare but then they put me in the back of a pickup truck and took me here.''

She gestures contemptuously at the cinder-block jail. Surrounded by the high prison wall, the women's quarters are little more than a big garage with a large open bay door and most of the glass broken out of the windows. There is no heat in the winter, no furniture, and until a priest managed several months ago to wrangle some discarded mattresses from a hotel, there were no beds. The prison doesn't provide blankets, toilet paper, soap, or eating utensils of any kind.

In order to eat the watery ''soup'' ladled out three times a day, prisoners must scavenge in the garbage for styrofoam cups or other containers -- no container, no food. But still they're luckier than their counterparts in other Mexican prisons. At Reysnosa, for example, deportees aren't fed at all.

''Why should we (feed them)?'' asks the director. ''They're never here more than 10 days.''

As soon as there are enough prisoners for a busload (between 35 and 50 people), the Salvadorans are bused out of Nogales - first to Mexico City and then to the southern border city of Tapachula, where they're abruptly set free with whatever money or possessions they may have left. The number of deportees dwindled as winter set in, but refugee workers in Mexico say that last summer 100 to 200 Salvadorans a week were being deported from Nogales alone. Each week a few Mexicans without proper identity papers were also deported, as were some fully documented Central Americans that the border patrol apparently mistook for Salvadorans.

Most refugees know the US isn't going to welcome them with open arms. What they sometimes don't realize until too late is that Mexico is also blocking the way to its northern neighbor and deporting refugees -- even those traveling on valid Mexican visitor visas -- when they venture too far north.

Some Salvadorans awaiting deportation in Mexican jails say they were caught just over the US border and handed back to Mexico by US border guards for a speedy deportation.

Some say they were trapped in a three-way exchange: They paid a ''coyote'' or smuggler to get them to the US. The coyote then turned them in to US authorities , and the US gave them to Mexico. No one knows what the coyotes got for cooperating with their arch enemies, the border police.

The treatment Salvadorans get in Mexico is just Chapter 1 in the story of abuse to Salvadorans who try to flee their homeland, say some US lawyers, religious leaders, and volunteers who are working with refugees.